Many implantable pacing devices have an ability to acquire cardiac electrograms, sometimes referred to as intracardiac electrograms (IEGMs), as a sensing electrode may be positioned in the heart. For example, an implantable pacing device may acquire cardiac electrograms using a case electrode (i.e., case of the device) and a sensing/pacing electrode positioned in the right ventricle. Where the device is implanted in a pectoral pocket, such a “unipolar” sensing configuration may span a distance of over 10 cm. The distance between electrodes in combination with the substantial surface area of the case electrode, make unipolar sensing configurations susceptible to interference from everyday changes in patient physiology. Consequently, useful information contained in the cardiac electrograms may be obscured.
As described herein, various techniques aim to increase usefulness of cardiac electrograms by accounting for patient physiology (e.g., patient position, changes in position, respiration, etc.). Through application of such techniques, information contained in cardiac electrograms may be used for a variety of diagnostics, including hear failure. Further, such diagnostics or information may be used to adjust therapy delivered, for example, by an implantable stimulation device.